Full-Stack Developer - AI Trainer (Spain)

Anyone AI Inc.; España; Remote; EUR 55,000 - 124,000; Part time

Job summary

Anyone AI Inc. is actively seeking skilled Full-Stack Developers to collaborate on a project with a leading AI lab. This remote, part-time, project-based consultant role offers flexible scheduling and task-based compensation.

Contributors will design and evaluate coding tasks, write specifications, extend test suites, and review peer submissions for quality and realism. You control your schedule and may work with multiple vendors.

Qualifications

• Advanced proficiency in English
• 3-7 years of professional software engineering experience
• Proficient in Python and JavaScript/TypeScript; working knowledge of Java, C#, or Go
• Backend or full-stack development experience in production systems
• Experience with testing frameworks (pytest, Jest, JUnit, xUnit, Go testing)
• Proven ability to debug and navigate large, multi-file codebases
• Experience with code reviews, refactoring, and production migrations

Responsibilities

• Design and implement multi-file coding tasks across bug fixing, feature development, refactoring, and testing
• Write clear natural-language specifications and reference implementations
• Develop and extend unit and integration test suites
• Review peer-generated tasks for correctness, clarity, and realism
• Identify edge cases, ambiguities, and potential failure modes
• Ensure alignment between specifications, code, and expected outputs

Skills

Python

JavaScript/TypeScript

Java

C#

Go

Backend development

Full-stack development

Testing frameworks

Debugging

Code reviews

Refactoring

Job description

Anyone AI is recruiting skilled Full-Stack Developers to work on a project with a leading AI lab.

Qualifications:

• Advanced professional written proficiency in English

• 3-7 years of professional software engineering experience

• Strong proficiency in Python and JavaScript/TypeScript; working knowledge of Java, C#, or Go

• Backend or full-stack development experience in production systems

• Experience with testing frameworks (e.g., pytest, Jest, JUnit, xUnit, Go testing)

• Proven ability to debug and navigate large, multi-file codebases

• Experience with code reviews, refactoring, and production migrations

Engagement:

Part-time, project-based expert evaluation work

Work Type:

Remote

Contributors will design and evaluate realistic software engineering tasks, including bug resolution, feature implementation, refactoring/migration, and test generation. Work includes both creating complex coding scenarios and reviewing peer submissions for quality and accuracy.

This is a project-based consultant role. Consultants will be paid on a per-project basis; hourly rates are estimates based on anticipated completion time. Consultants control their own schedule, provide their own tools, and may simultaneously provide services to other vendors/employers (subject to those vendors' allowances).

Responsibilities:

Contributors will:

• Design and implement multi-file coding tasks across bug fixing, feature development, refactoring, and testing

• Write clear natural-language specifications and reference implementations

• Develop and extend unit and integration test suites

• Review peer-generated tasks for correctness, clarity, and realism

• Identify edge cases, ambiguities, and potential failure modes

• Ensure alignment between specifications, code, and expected outputs

Expected Outcomes:

• High-quality, production-realistic coding tasks

• Complete and correct reference implementations

• Robust test coverage and validation artifacts

• Structured, actionable peer review feedback